The correct answer is: B. Iris.
The iris is the colored part of the eye that controls the amount of light that enters the eye. It does this by contracting and dilating the pupil, which is the black hole in the center of the iris. When there is a lot of light, the iris contracts to make the pupil smaller. This reduces the amount of light that enters the eye and prevents it from being overstimulated. When there is not enough light, the iris dilates to make the pupil larger. This allows more light to enter the eye and improve vision.
The retina is the light-sensitive tissue at the back of the eye. It converts light into electrical signals that are sent to the brain, which interprets them as images. The cornea is the clear front part of the eye that helps to focus light on the retina. The lens is a transparent structure behind the iris that helps to focus light on the retina.
I hope this helps! Let me know if you have any other questions.